  Air Liquide Australia Limited
Products and Services Properties of Industrial and Medical Gases
 Gases may be classified in various ways, according to how they are used. For example, we may distinguish the following types:
The air in which we live consists of a mixture of various gases, including: oxygen (which sustains life), nitrogen, argon, neon, krypton and xenon. But air also contains various impurities such as carbon dioxide or hydrogen traces, as well as suspended matter such as very small water droplets, dust, pollen or heavy vapors, such as gaseous hydrocarbons. These "impurities" are removed by filtration or adsorption systems, before air is separated into its various components. Oxygen is by far the most common element found in nature. For example, did you know that oxygen makes up by weight:
For more information, click on applications. Nitrogen is mainly found in the atmosphere, where it accounts for 78% of the air we breath by volume. But nitrogen is also found:
For further information, click on applications. The atmosphere contains about 0.9% argon. A neutral and colorless gas like nitrogen, it does not however exist in nature other than in the air. It cannot sustain life, but it is highly used in certain industrial applications due to its high level of chemical inertness and the relative ease with which it can be produced. For further information, click on applications. Neon (Ne), Krypton (Kr) and Xenon (Xe) These three gases are known as "rare" gases, since combined they only account for one thousandth of the air which surround us. These colorless and tasteless gases cannot sustain life. They are so inert that they do not react and can only be combined with other chemical substances with great difficulty. Their extreme inertness makes them very valuable for certain applications. Carbon dioxide gas is formed from the combination of two elements: carbon and oxygen. It is produced from the combustion of coal or hydrocarbons, the fermentation of liquids and the breathing of humans and animals. Found in small proportions in the atmosphere, it is assimilated by plants which in turn produce oxygen. CO2 gas has a slightly irritating odor, is colorless and heavier than air. It cannot sustain life. It freezes at -78.5 C to form carbon dioxide snow. In an aqueous solution it forms carbonic acid, which is too unstable to be easily isolated. For further information, click on applications. Acetylene is not an air gas, but a synthesis gas generally produced from the reaction of calcium carbide with water. It was burnt in "acetylene lamps" to light homes and mining tunnels in the 19th century. A gaseous hydrocarbon, it is colorless, has a strong garlic odor, is unstable, highly combustible, and produces a very hot flame (over 3000 C or 5400 F) when combined with oxygen. For further information, click on applications. Propane is a fuel gas of the gaseous hydrocarbon family, produced from the distillation of oil. It is commonly used for heating purposes in central heating systems, hot water boilers and gas stoves. It is a colorless gas which is heavier than air but with practically no odor. Its presence may be easily detected by adding a strong and unpleasant smelling product during production. The common characteristic of these gases is that they contain both carbon atoms (which give the flame it's hot color when burnt) and hydrogen atoms which are particularly combustible. The most well-known gaseous hydrocarbons are:
Hydrogen is only found in the atmosphere at trace levels, but is abundant in hydrocarbons (petroleum and petroleum by-products) and especially in ordinary water where it constitutes the lightest fraction of the H2O molecule. Hydrogen gas is colorless, highly flammable, very light, cannot sustain life and reacts easily with other chemical substances. For further information, click on applications. Helium is highly abundant in the sun's atmosphere (hence its name), and at trace level in the Earth's atmosphere. However, it may be found in fossil form in natural gas pockets in some oil fields, where it is extracted by drilling deep into the subsoil of certain regions in such countries as the U.S.A., Algeria and Poland. Helium is an extremely light gas (its specific gravity is 0.14) and is therefore very volatile. It is colorless, odorless, non-flammable and completely inert. It cannot sustain life. For further information, click on applications. Ozone (O3) is formed by the combination of three oxygen atoms. An unstable gas with a strong and irritating odor (which explains its name), ozone is corrosive, a strong oxidant and very toxic. For all of these reasons it absolutely unsuitable to sustain life. Ozone is generally produced by generating high-power electrical discharges in the air or in oxygen. Found in the upper layers of the atmosphere, where it is formed by a photo-chemical reaction, ozone serves as a shield which protects our planet from the sun's ultraviolet radiation. Ozone is used to neutralize odors, sterilize water, bleach textiles and paper, and in certain chemical manufacturing processes. Carbon monoxide (CO) gas is formed from the combination of a carbon atom with an oxygen atom. Not only flammable, it is also very hazardous since it is very toxic and odorless. It cannot sustain life and is produced, among other things, from incomplete gas combustion due to lack of oxygen. It can therefore cause domestic accidents if heating systems are poorly maintained. It is produced on a large scale in industry, in combination with hydrogen, by reforming hydrocarbons, generally natural gas. It is used in large quantities to produce various intermediary organic chemicals, such as acetic acids, isocyanates, formic acid, and also certain polymers such as polycarbonates and polycetones. Some examples of other gases commonly used in industry are:
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